Flexible Metal/Oxide/Metal Transparent Electrodes Made of Thermally Evaporated MoO3/Ag/MoO3 for Thin Film Heaters

The authors report on thermally-evaporated MoO3/Ag/MoO3 multilayer films as a flexible and transparent electrode for high performance flexible thin film heaters (TFHs). Using thermal evaporation, the authors obtain highly flexible MoO3/Ag/MoO3 multilayer films on colorless polyimide substrate without plasma damage. To optimize the thickness of the Ag interlayer, the authors investigate the electrical, optical, morphological, and mechanical properties of MoO3/Ag/MoO3 multilayers as a function of Ag interlayer thickness. Based on a figure of merit value, the authors obtain an optimal MoO3/Ag/MoO3 electrode with a low sheet resistance of 3.17 Ohm/square, a high optical transmittance of 77.85%, and critical bending radius of 1 mm, which are acceptable for fabrication of TFHs. The flexible TFHs (25 x 25 mm(2)) fabricated on a thermally evaporated MoO3/Ag/MoO3 electrode shows a high saturation temperature of 118 degrees C even at a low input power of 2.5 W (input voltage 2.5 V) due to very low sheet resistance. Successful operation of the flexible TFHs indicate that the thermally-evaporated MoO3/Ag/MoO3 film is a promising alternative transparent electrode to substitute sputtered Sn-doped In2O3 (ITO) films for highly transparent and flexible TFHs.